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At least 145 records · Page 8Linked to original sources
PubMed2000

Phytosulfokine-alpha, a peptide growth factor found in higher plants: its structure, functions, precursor and receptors.

Phytosulfokine-alpha, a sulfated pentapeptide growth factor universally found in both monocotyledons and dicotyledons, strongly promotes proliferation of plant cells in culture. It is similar to animal polypeptide hormones in that it is processed from a larger precursor, preprophytosulfokine, although the putative processing sites do not conform to consensus sequences for endoproteolytic processing sites flanking animal prohormones. Like the animal preprohormones, preprophytosulfokine also has a signal peptide at the N-terminus for targeting to secretory pathways. The preprophytosulfokine gene has been confirmed to be expressed in vivo as well as in vitro.

Amino Acid Sequence↗
PubMed2000

Evaluating environmental contamination in Ria Formosa (Portugal) using stress indexes of Spartina maritima.

Species of Spartina are potentially useful for biomonitoring coastal systems because they are abundant in the intertidal and have a wide geographic distribution in temperate zones. In this study, three indexes of physiological stress, thiolic protein concentration, adenylic energy charge (AEC) index [AEC = ATP + 0.5ADP/(ATP + ADP + AMP)] and photosynthetic efficiency (Fv/Fm), are measured in Spartina maritima plants collected at four sites and compared with metal concentrations in the sediments and Spartina tissues. Two sites were close to urban centers and two were located further away, in less contaminated areas. Concentrations of copper, cadmium, lead and zinc were determined by atomic absorption spectrophotometry, thiolic proteins were determined by polarography and adenilic nucleotides were determined by high performance liquid chromatography. Photosynthetic efficiencies were measured with a fluorometer. The sediments of sites closer to urban centers had higher concentrations of metals than the sites located further away. Metal concentration within plants did not follow this spatial pattern, probably due to spatial differences in metal bioavailability, uptake rates, internal transport and excretion processes. Concentrations of all metals studied were higher in underground plant structures than aerial, except cadmium whose levels were not significantly different. On the other hand, the stress indexes followed the spatial pattern of metals in the sediment. Thiolic protein concentrations were higher in plants from polluted sites, and were three to four times higher in aerial than in underground plant structures. Leaf AEC ratios and photosynthetic efficiencies were lower in plants from polluted sites indicating that they were growing under stressful conditions. We conclude that the use of these indexes in S. maritima represent a useful tool to monitor contamination in Ria Formosa lagoon as they provide an integrated measure of the toxicological burden of contamination.

Environmental Monitoring↗
PubMed2007

Microscopic examination of changes of plant cell structure in corn stover due to hot water pretreatment and enzymatic hydrolysis.

Particle size associated with accessible surface area has a significant impact on the saccharification of plant cell walls by cellulolytic enzymes. Small particle sizes of untreated cellulosic substrate are more readily hydrolyzed than large ones because of higher specific surface area. Pretreatment enlarges accessible and susceptible surface area leading to enhanced cellulose hydrolysis. These hypotheses were tested using ground corn stover in the size ranges of 425-710 and 53-75 microm. Ultrastructural changes in these particles were imaged after treatment with cellulolytic enzymes before and after liquid hot water pretreatment. The smaller 53-75 microm corn stover particles are 1.5x more susceptible to hydrolysis than 425-710 microm corn stover particles. This difference between the two particle size ranges is eliminated when the stover is pretreated with liquid hot water pretreatment at 190 degrees C for 15 min, at pH between 4.3 and 6.2. This pretreatment causes ultrastructural changes and formation of micron-sized pores that make the cellulose more accessible to hydrolytic enzymes.

Cellulase↗
PubMed1992

Oligouronide signaling of proteinase inhibitor genes in plants: structure-activity relationships of Di- and trigalacturonic acids and their derivatives.

Polygalacturonic acid (DPave approximately 20), alpha-1,4-di- and trigalacturonic acids, delta 4,5-alpha-1,4-di- and delta 4,5-alpha-trigalacturonic acids, and several chemically modified derivatives of these oligomers were prepared. Their proteinase inhibitor-inducing activities were determined by supplying solutions of the compounds to young, excised tomato plants through their cut stems. Digalacturonic acid, on a molar basis, was the most active oligomer (ED50 approximately 1.5 micrograms/plant), being about three times more active than the parent oligogalacturonic acid (ED50 approximately 5.5 micrograms/plant). The specific inducing activity of trigalacturonic acid was about half that of digalacturonic acid. Both delta 4,5-di- and delta 4,5-trigalacturonic acids were about half as active as di- and trigalacturonic acids, respectively. Reduction of the hemiacetal (carbonyl) group of the di- and trigalacturonic acids with sodium borohydride completely destroyed proteinase inhibitor inducing activities, indicating that the inducing activity of both acids depends upon an intact hemiacetal at the reducing termini. Reduction of the double bonds of delta 4,5-di- and delta 4,5-trigalacturonic acids by catalytic hydrogenation with H2 (palladium catalyst) produced derivatives with specific inducing activities of approximately one-half that of the parent compounds. Thus, while the reducing termini of oligogalacturonides require an intact hemiacetal for proteinase inhibitor inducing activities, the nonreducing termini of the small oligouronides do not require a C4 hydroxyl nor a C5 proton to be active inducers.

Carbohydrate Conformation↗
PubMed1989

Structure of Plant Cell Walls : XXVI. The Walls of Suspension-Cultured Sycamore Cells Contain a Family of Rhamnogalacturonan-I-Like Pectic Polysaccharides.

Considerable information has been obtained about the primary structures of suspension-cultured sycamore (Acer pseudoplatanus) cell-wall pectic polysaccharides, i.e. rhamnogalacturonan I, rhamnogalacturonan II, and homogalacturonan. However, these polysaccharides, which are solubilized from the walls by endo-alpha-1,4-polygalacturonase, account for only about half of the pectic polysaccharides known to be present in sycamore cell walls. We now report that, after exhaustive treatment with endo-alpha-1,4-polygalacturonase, additional pectic polysaccharides were extracted from sycamore cell walls by treatment with Na(2)CO(3) at 1 and 22 degrees C. These previously uncharacterized polysaccharides accounted for approximately 4% of the cell wall. Based on the glycosyl and glycosyl-linkage compositions and the nature of the products obtained by treating the quantitatively predominant NaCO(3)-extracted polysaccharides with lithium metal dissolved in ethylenediamine, the polysaccharides were found to strongly resemble rhamnogalacturonan I. However, unlike rhamnogalacturonan I that characteristically had equal amounts of 2- and 2,4-linked rhamnosyl residues in its backbone, the polysaccharides extracted in Na(2)CO(3) at 1 degrees C had markedly disparate ratios of 2- to 2,4-linked rhamnosyl residues. We concluded that polysaccharides similar to rhamnogalacturonan I but with different degrees of branching are present in the walls of suspension-cultured sycamore cells.

Journal Article↗
PubMed1982

Synthesis of brassinosteroids and relationship of structure to plant growth-promoting effects.

A number of brassinosteroids with and without hydroxyl groups or an alkyl substituent in their side chain were synthesized. The alkyl substituent at C-24 highly influenced the oxidation of the C-22 double bond with osmium tetroxide and, hence the ratio of the 22 beta,23 beta- and 22 alpha,23 alpha-glycolic isomers obtained. Two different bean bioassays used to compare the plant growth-promoting capabilities of these compounds and of brassinolide and its three side chain 22,23-cis-glycolic isomers showed that brassinolide was the most active. The next most active brassinosteroids were generally those with 22 alpha-OH, 23 alpha-OH orientation and a beta-methyl or alpha-ethyl substituent at C-24. Similarly, of the synthetic precursor tetrahydroxy ketones of the brassinosteroids, those with 22 alpha-OH, 23 alpha-OH orientation (like brassinolide) and an alkyl group at C-24 were also the most active in both bioassays. The results indicate stringent structural features are required for a steroid to induce brassin activity. The structural requirements are: a trans A/B ring system (5alpha-hydrogen), a 6-ketone or a 7-oxa-6-ketone system in ring B, cis alpha-oriented hydroxyl groups at C-2 and C-3, cis hydroxy groups at C-22 and C-23 as well as a methyl or ethyl substituent at C-24.

Biological Assay↗
PubMed1987

The effect of pH on the conformation and stability of the structure of plant toxin-ricin.

The effect of pH on the conformation of ricin and its A- and B-chains has been studied by measuring their intrinsic fluorescence. At pH 5.0 and 7.5, the structural stability of toxin and subunits was estimated according to the denaturing action of guanidine hydrochloride. It was demonstrated that the fluorescence of native toxin and catalytic A-subunit does not depend significantly on pH in the range pH 3-8, whereas ricin B-chain undergoes a structural transition at pH less than 5.0. The structural stability of ricin and isolated chains differs significantly at pH 7.5 and 5.0; the structural stability of ricin and the A-chain increases, whereas that of the B-chain decreases.

Hydrogen-Ion Concentration↗
PubMed1980

Structure of Plant Cell Walls: XI. GLUCURONOARABINOXYLAN, A SECOND HEMICELLULOSE IN THE PRIMARY CELL WALLS OF SUSPENSION-CULTURED SYCAMORE CELLS.

The isolation, purification, and partial characterization of a glucuronoarabinoxylan, a previously unobserved component of the primary cell walls of dicotyledonous plants, are described. The glucuronoarabinoxylan constitutes approximately 5% of the primary walls of suspension-cultured sycamore cells. This glucuronoarabinoxylan possesses many of the structural characteristics of analogous polysaccharides that have been isolated from the primary and secondary cell walls of monocots as well as from the secondary cell walls of dicots. The glucuronoarabinoxylan of primary dicot cell walls has a linear beta-1,4-linked d-xylopyranosyl backbone with both neutral and acidic sidechains attached at intervals along its length. The acidic sidechains are terminated with glucuronosyl or 4-O-methyl glucuronosyl residues, whereas the neutral sidechains are composed of arabinosyl and/or xylosyl residues.

Journal Article↗
PubMed1999

Differential effects of plant species on a mite pest (Tetranychus utricae) and its predator (Phytoseiulus persimilis): implications for biological control.

The influence of plant species on the population dynamics of the spider mite pest, Tetranychus urticae, and its predator, Phytoseiulus persimilis, was examined as a prerequisite to effective biological control on ornamental nursery stock. Experiments have been done to investigate how the development, fecundity and movement of T. urticae, and the movement of P. persimilis were affected by plant species. A novel experimental method, which incorporates plant structure, was used to investigate the functional response of P. persimilis. Development times for T. urticae were consistent with published data and did not differ with plant species in a biologically meaningful way. Plant species was shown to have a major influence on fecundity (P < 0.001) and movement of the pest mite (P < 0.01), but no influence on the movement of the predator. The movement of both pest and predator was shown to be related to the density of the adult pest mites on the plant (P < 0.001). Plant structure affected the functional response, particularly in relation to the ability of the predator to locate prey at low densities. The impact of these findings on the effective use of biological control on ornamental nursery stock is discussed.

Animals↗
PubMed2001

Chlamydocin analogues from the soil fungus Peniophora sp.: structures and plant growth-retardant activity.

Three chlamydocin analogues that show activity for reducing the height of rice seedlings without blotch and wilting were isolated from the culture filtrate of the soil fungus Peniophora sp. and were characterized by spectral data and chemical conversion. For two of these, it is their first isolation as natural products. The proposed role of the functional groups of the 2-amino-8-oxodecanoic acid moiety of these analogues is discussed in terms of growth retardant activity.

Basidiomycota↗